Running Losses 3/2 Way Valve

Running losses refers to the fuel vapors that can escape to the atmosphere during vehicle operation. The fuel tank is the major source of running loss vapors. The redesigned fuel pressure regulator with by-pass solenoid was introduced on the 1995 325i and as of the 98 model year is equipped on all vehicles.

With the engine running, the volume of fuel flowing through the fuel rail is more than the engine can consume. The fuel passing through the fuel rail is heated by the engine and is returned to the tank.

Using the by-pass type regulator reduces the fuel heating thereby reducing the temperature of the fuel in the tank. This lowers the amount of vaporization that takes place.

OPERATION:

3/2 Way Valve (Running Losses):

The engine control module controls the operation of the by-pass solenoid.







The solenoid is energized for 20 seconds on engine start up to purge air bubbles.








After twenty seconds, the solenoid is switched OFF and the bypass is opened.

The fuel injectors are provided with regulated fuel for injection but all of the returned fuel by-passes the engine compartment fuel rail thus lowering the temperature and amount of vaporization that takes place in the fuel tank.

The solenoid is also activated momentarily if an engine misfire is detected. This function provides full fuel flow through the fuel rail to determine if the misfire was caused by a lean fuel condition.